The effect of interferon on DNase and RNase expression in Friend erythroleukemia cells and in other cells in tissue culture is being investigated. Interferon causes equal 2-4 fold increases in 5 major intracellular DNase activities. The pattern of expression in these cells in the presence or absence of interferon closely resembles the DNase expression in peripheral leukocytes from human donors with CML. Induction of differentiation in Friend cells results in reversion of the "abnormal DNase pattern" to a pattern that closely resembles that observed in normal mouse or human peripheral leukocytes. Initial experiments indicate that DNase and RNase expression may serve as a marker for the differentiation status of these cells. Preliminary results suggest that changes in DNases may indicate whether or not the induction of differentiation affects the interferon induced state in these cells, whether interferon affects the DMSO induced differentiation of these cells and whether the DNases are involved in the process of differentiation and in the antiviral state. Studies on the effects of interferon therapy for malignancy in humans on nuclease expression in leukocytes are underway in collaboration with the Clinical Oncology Branch.